For ease of explanation, the guidance and placement and ongoing maintenance of a catheter for enteral nutrition will be described in one example in this specification. It will however be clear to the person skilled in the art that the techniques and equipment described are useful for similar placement requirements in other parts of the human body and animal bodies as well. Catheters are used for many different purposes and there exist many different catheter types. An example of the use of the invention in a human body will also be provided in the field of Central Venous Catheter location.
Enteral nutrition includes both the ingestion of food orally and the non-volitional delivery of nutrients by tube into the gastrointestinal tract. Patients are candidates for enteral tube feeding that will not, should not, or cannot eat but who have a functional gastrointestinal tract. Benefits of enteral tube feeding are the maintenance of gastrointestinal structure and functional integrity, enhanced utilization of nutrients, ease and safety of administration.
Enteral tube feeding is contraindicated for patients with diffuse peritonitis, intestinal obstruction that prohibits use of the bowel, intractable vomiting, paralytic ileus, and/or severe diarrhea that makes metabolic management typical. Other potential contraindications that depend on the clinical circumstances include severe pancreatitis, enterocutaneous fistulae, and gastrointestinal ischemia. Enteral tube feeding is not recommended during the early stages of short-bowel syndrome or in the presence of severe malabsorption.
The route selected for tube feeding depends upon the anticipated duration of feeding, the condition of the gastrointestinal tract (e.g. esophageal obstruction, prior gastric or small-bowel resections), and the potential for aspiration. The intestine can be accessed at the bedside (naso intestinal tube, naso endoscopic gastrostomy) or in the operating room (gastrostomy and jejunostomy).
Nasal intubation for gastric feeding is the simplest and most often used method for tube feeding. This technique is preferred for patients who are expected to eventually resume oral feeding. Maximal patient comfort and acceptance is more likely when a soft feeding tube with a small external diameter is used. Access to the duodenum and jejunum is possible with longer tubes but placement of the tip into the duodenum and jejunum is more difficult and time consuming and has added risk factors.
Enteral tube feeding is considered safer than parenteral nourishment because mechanical, infection, and metabolic complications are usually less severe than those encountered with parenteral nutrition. However, enteral feeding is not problem free, and significant complications can occur when the tube and feeding is managed by unskilled or untrained individuals or if monitoring is absent or inappropriate.
Incorrect placement of the feeding tube is one of a number of major complications. Most serious is the unintended placement of the catheter during nasal intubation into the cardiovascular system or into the lungs. Both of these situations are possible when inexperienced medical staff perform intubation. A stylet (relatively stiff small gauge wire) is used to stiffen and support the otherwise flaccid catheter tube during its intubation.
It is also prudent to check that the exit aperture of the feeding tube (typically located at the distal end/tip of the tube) remains in its desired location over the period of feeding. Protocols that address this requirement include frequent monitoring for the appropriate pH of fluids extracted from the feeding tube while not carrying nutritional liquids and careful patient monitoring to ensure that nutritional uptake is as expected.
X-rays are often used to determine the location of the caudal/distal end of the tube. However, even X-rays are not necessarily conclusive as to its location. The natural and continuous movement of the internal organs can make it difficult for the physician interpreting the X-ray to be sure of the actual location of the caudal/distal end of the tube because the movement described can change the position of the catheter over time.
There exist a large variety of catheters, their names sometimes indicating their use, the part of the body they enter or treat and sometimes they are named after the physician or physicians who developed methodologies for their use.
This invention also relates to catheter location methods and means for central venous catheters.
Intravenous catheters are those that access the interior of a patient via an opening in the skin passed down one or more of the many branches of the venous system to the region requiring medical attention. These types of catheters are also referred to as Venous Access Catheters (VAC) and Central Venous Catheters (CVCs) and are used generally in the cardiovascular system.
A sub-category of intravenous catheters is those that fall under the heading of Peripherally Inserted Central Catheter (PICC). These catheters have been used by clinicians for many years and many different techniques exist for their insertion.
One such insertion technique is the Seldinger technique and along with advances in devices and materials there now exists a modified Seldinger technique, useful particularly for small or poor veins.
There exist a large selection of intravenous catheters such as for example peripheral catheters which are used for insertion into the body that are from one half to three inches in length; midline catheters which are used for insertion being greater than three inches in length; mid-clavicular and non-tunneled sub-clavian, tunneled Groshong, Hickman and Broviac or subcutaneous implanted ports for longer lengths.
Common to intravenous catheters is the use of a guide wire that is passed into the body and into a vein and then directed by the skill of the clinician to the desired location. Once the guide wire is in place a catheter is slid over its external free end and pushed till the distal end of the catheter reaches the end of the guide wire.
The location of the tip of these types of catheters or the recordal of the advancement of the guide wire into the body is achieved in a number of ways.
Return checks are used to expire types of liquids expected to be at or near the tip of the catheter and the checking of length markings on the wires used within catheters are two methods used by clinicians who do not have ready access to alternatives. Ultrasound guidance, fluoroscopy and X-ray methodologies are preferred even though they do not always provide an exact determination of the location of the tip or path of the guide wire or catheter.
More expensive and more time-consuming CT examinations provide the best means of locating not only the tip but also the path of any of the types of catheter described above and others that are located in the body of a patient.
The final location of the caudal/distal end of any catheter is critical to the efficacy of the purpose for the use of the catheter. In one example, the delivery of drugs directly into the heart can be best achieved by the location of the caudal/distal end of the catheter in the superior vena cava (CVC). Studies show that it is preferable to locate the caudal/distal end of the catheter in the upper portion of the superior vena cava (typically recognised as being more than 4.5 cm above the cavoatrial junction). Studies indicate that these preferable locations appear to minimise catheter malfunction.
More critical however, is to ensure that the catheter is in the superior vena cava itself, as there exist studies indicating that there is a significant association between catheter malfunction and catheter tip location in the venous system adjacent to the superior vena cava.
FIG. 7 depicts the various veins in the vicinity of and including the superior vena cava.
Where for example, the catheter tip is in either of the brachiocephilac veins or near the junction of a brachiocephilac vein there is a greater likelihood of the unwanted development of a fibrin sheath or the presence of thrombus around or at the tip of the catheter as compared to catheter tips located in the superior vena cava. Greater likelihood of unwanted developments can occur when a catheter tip is located in the sub-clavian vein or the cavoatrial junction or in the right atrium.
The effect of inappropriate or less than ideal catheter tip location is shortened survival which clearly is manageable but more serious effects may include thrombosis and phlebitis infections more, particularly pheumothorax infections and, in more serious situations, occlusions.
When catheter tips suffer thrombosis, these studies demonstrate significantly shorter survival than those catheters that are not subject to this unwanted development.
Appropriate patient care requires consideration of a large number of factors when considering the need for intravenous catheter usage. Sometimes the benefit of drug delivery has to be carefully weighed against the likelihood of adverse effects of intravascular device related infections as mentioned previously.
Catheter selection is not a simple matter and factors to be considered include the following:                type of medication        osmolarity and pH of the solution to be infused        duration of therapy required        secondary risk factors and chronic diseases        patient age, activities, work and lifestyle        future intravenous needs and long term prognosis        current availability and status of access veins (typically peripheral veins of the limbs)        patient history of neurologic impairments, surgeries affecting veins or lymphatic system, bloods dyscrasias, thrombosis and previous intravenous use history        current patient diagnosis and preferences for treatment.        
The anticipated duration of therapy can readily suggest short peripheral catheters for periods of less than five days, and for periods of less than four weeks a midline catheter is generally suitable.
Midclavicular lines are an option and becoming more popular as the occurrence of thrombosis resulting from sub-optimal placement in sub-clavian regions other than the superior vena cava increase.
In fact mid-clavicular lines are often used in home care situations to avoid the time and cost of confilinatory X-rays. However, even mid-clavicular lines need to be optimally placed in the lower one third of the superior vena cava, close to the junction of the superior vena cava and the right atrium but should not advance into the right atrium itself.
The previously mentioned Peripherally Inserted Central Catheters (PICCs) having a tip location in the superior vena cava can be used for long term therapy (five days to one year). However, they should be critically checked by X-ray to determine appropriate tip placement even though this is neither a totally satisfactory nor certain method of location checking.
It is thus a real need for physicians to be able to increase their confidence that the catheter has been placed at the desired location and remain there in the body of their patient. This is so whether that is for the purpose of enteral and parenteral nutrition, receiving vesicant chemotherapeutic agents, antibiotics and blood sampling or for other purposes.